   (if (empty? s)
     nil
     (if (= (first s) c)
-      (clojure.contrib.string/drop 1 s)
-      (let [remain (string-remove-char (clojure.contrib.string/drop 1 s) c)]
+      (.substring s 1 (count s))
+      (let [remain (string-remove-char (.substring s 1 (count s)) c)]
         (if (nil? remain)
           nil
           (str (first s) remain))))))

(ns examples.string
  (:require [clojush] [clojure.contrib.math])
  (:use [clojush] [clojure.contrib.math]))

; Tries to get a string with the most unique characters. If there are at least goal, succeeds.
#_(pushgp :error-function (fn [program]

                       1)
                    s1
                    s2))
     (abs (- (count s1) (count s2)))))

(defn string-remove-char
  "Returns s with first instrance of c removed, if c is in s. Otherwise, returns nil"
